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Green fingerprints

19 October 1996

CATCHING criminals can damage the ozone layer. But police forces may soon
be able to put that right by abandoning the CFCs used to enhance fingerprints on
porous surfaces such as paper.

CFC 113 is used as a solvent for a chemical reagent called ninhydrin, which
reacts with amino acids in fingerprints to give a purple stain. The formulation,
which also includes ethanol and acetic acid, has more than doubled the number of
prints identified.

After testing thousands of fraudulent cheques, British forensic scientists
have now shown that a modified version of the current formulation which uses
hydrofluorocarbons instead of CFCs does the job just as well.

Under the Montreal Protocol, which bans the use of CFCs in developed
countries, law enforcement agencies have an exemption. But supplies of CFCs are
dwindling.

“We have been receiving calls from police forces all over the world who are
desperate to find an alternative,” says Terry Kent, who works for the Home
Office’s Police Scientific Development Branch.